1. Field of the Invention
The present invention relates to a magnetic tape apparatus capable of recording or reproducing information with respect to a magnetic tape.
2. Description of Related Art
Recently, the amount of data dealt with in a computer system is increasing more and more along with the increase in a capacity of a hard disk. Therefore, the demand for a data backup system using a magnetic tape also is increasing. In such a data backup system, a linear magnetic tape apparatus is mounted.
A head used in the linear magnetic tape apparatus includes a member called a “rail” in an elongated shape in a tape width direction so that the rail comes into contact with an entire region of a magnetic tape in a width direction even when the head is moved between tracks. For example, a magnetic head of a linear tape open (LTO) type has a first rail and a second rail. The first rail and the second rail are arranged side by side in a transport direction of the magnetic tape so that the respective longitudinal directions are substantially perpendicular to the transport direction of the magnetic tape. A first magnetic element is mounted on the first rail, which performs a recording operation when the magnetic tape is transported in one direction and performs a reproduction operation when the magnetic tape is transported in the other direction. A second magnetic element is mounted on the second rail, which performs a recording operation when the magnetic tape is transported in the other direction and performs a reproduction operation when the magnetic tape is transported in the one direction.
Furthermore, the magnetic head may include a plurality of third rails on which magnetic elements are not mounted, in addition to the first and second rails as described above. The third rails are placed on a magnetic tape input side or output side in the first and second rails so that tape sliding surfaces of the third rails are substantially flush with tape sliding surfaces of the first and second rails. Furthermore, the third rails can stabilize the relative position of the magnetic tape with respect to the magnetic head when the magnetic tape is in contact with the magnetic head, and keep the contact state between the magnetic tape and the first and second rails in a stable state. Furthermore, the third rails can remove foreign matter adhering to the surface of the magnetic tape. Thus, the third rails can prevent the foreign matter from entering between the rails and the magnetic tape to inhibit recording and reproduction operations. Patent Document 1 (JP 2006-127730 A) discloses a magnetic head with a configuration as described above.
The recording wavelength of the magnetic tape is decreased along with the further increase in a recording capacity, and the surface of the magnetic tape is being smoothened so as to suppress the degradation in the recording and reproduction characteristics caused by spacing. When the surface of the magnetic tape is smoothened, the contact area between the magnetic head and the magnetic tape increases to enhance a friction coefficient therebetween. When the friction coefficient increases, the magnetic tape moves in the tape width direction, following the movement of the magnetic head in the tape width direction by a tracking servo control and the like, with the result that the tracking operation of the magnetic head becomes unstable.
FIG. 5A shows a state before the magnetic head is moved, and FIG. 5B shows a state after the magnetic head is move by the tracking servo control. When a magnetic head unit 101 is moved in a direction represented by an arrow X from the state shown in FIG. 5A, a magnetic tape 5 is moved in the direction represented by the arrow X by the friction force between a sliding surface 101a and the magnetic tape 5, as shown in FIG. 5B.